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Date: Thu, 9 Jul 2026 08:09:59 +0200
From: Christoph Hellwig <hch@lst.de>
To: Yu Kuai <yukuai@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>, Tejun Heo <tj@kernel.org>,
	Christoph Hellwig <hch@lst.de>, Keith Busch <kbusch@kernel.org>,
	Sagi Grimberg <sagi@grimberg.me>, Alasdair Kergon <agk@redhat.com>,
	Benjamin Marzinski <bmarzins@redhat.com>,
	Mike Snitzer <snitzer@kernel.org>,
	Mikulas Patocka <mpatocka@redhat.com>,
	Dongsheng Yang <dongsheng.yang@linux.dev>,
	Zheng Gu <cengku@gmail.com>, Coly Li <colyli@fygo.io>,
	Kent Overstreet <kent.overstreet@linux.dev>,
	Josef Bacik <josef@toxicpanda.com>, Yu Kuai <yukuai@fygo.io>,
	Nilay Shroff <nilay@linux.ibm.com>, linux-block@vger.kernel.org,
	cgroups@vger.kernel.org, linux-nvme@lists.infradead.org,
	dm-devel@lists.linux.dev, linux-bcache@vger.kernel.org
Subject: Re: [RFC PATCH v1 00/17] blk-cgroup: protect blkgs with blkcg_mutex
Message-ID: <20260709060959.GA16504@lst.de>
References: <20260704195124.1375075-1-yukuai@kernel.org>
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User-Agent: Mutt/1.5.17 (2007-11-01)

On Sun, Jul 05, 2026 at 03:51:07AM +0800, Yu Kuai wrote:
> From: Yu Kuai <yukuai@fygo.io>
> 
> This RFC moves queue-local blkg topology synchronization from
> q->queue_lock to q->blkcg_mutex.
> 
> q->queue_lock is a hot block-layer spinlock used by request queue runtime
> paths,

I don't think it is hot any more.  If it is in one of your workloads
we have a deep problem somewhere.  That being said, futher removing
uses of his old catch-all lock is always good, hopefully we can
eventually remove it entirely.

So this series looks great to me conceptually, but I'm unfortunately
not a very qualified reviewer for the blk-cgroup code.